1. Field of the Invention
This invention relates to an apparatus and method for supporting the interior of appliance cabinets during molding, and more particularly to an apparatus and method for simultaneously supporting each of the interior walls of an appliance cabinet during the injection and curing of foam insulation between a cabinet inner wall and outer wall.
2. Description of Related Art
Many types of appliance cabinets, such as refrigerators and freezers, employ insulation surrounding the interior thereof to help maintain a desired internal temperature. Generally, such cabinets comprise a rear wall with depending side walls, wherein such walls have inner and outer surfaces with a small cavity therebetween. Insulating foam is injected into the cavity between the inner and outer surfaces of the rear and side walls.
Insulating foam is injected into the cabinet cavity under high pressure and expands during curing within the cabinet cavity. This pressure tends to cause bulging of the internal and external walls of the cabinet. Accordingly, it is known in the art to employ shoring panels adjacent the internal and external cabinet surfaces, during injection and curing, to prevent such bulging. Such an apparatus is disclosed in U.S. Pat. No. 3,801,059. During insulation injection and curing, shoring panels are secured flush against the interior and exterior cabinet surfaces so as to provide sufficient additional support strength to the cabinet surfaces to resist bulging. Upon completion of the curing process, the shoring panels are removed from the cabinet surfaces so that the insulated cabinet can be transported away and another cabinet brought into position for insulation injection utilizing the aforementioned shoring members.
It is also known to provide shoring apparatus, such as that disclosed in U.S. Pat. No. 3,801,059, that can be retracted away from the cabinet walls between insulations to accommodate removal and insertion of cabinets, and expanded during insulation injection and curing to provide shoring support to the cabinet walls. One major shortcoming of such designs is that only two interior side walls can be shored at one time. Thus, with such apparatus it is currently necessary to inject and cure only two side walls, remove the partially insulated cabinet from the apparatus, reinsert the cabinet in another apparatus, and inject and cure insulation in the two remaining side walls. It is desirable to employ a single apparatus capable of providing shoring support to all internal cabinet surfaces simultaneously, so that only a singular injection and curing step is necessary to insulate the entire cabinet cavity.
It is also known in the art to employ separate shoring apparatus to support the internal and external surfaces. An expandable plug or core is placed into the internal area of the cabinet to be insulated to provide support to the interior walls. However, current plug designs for simultaneously shoring all four depending side walls, such as the apparatus disclosed in U.S. Pat. No. 4,370,795, do not provide support at the corners whereat the depending side walls meet. Thus, a problem associated with current plugs is that they allow bulging at corner sections due to the foam injection pressure and expansion during curing within the cabinet cavity which, in combination with lack of shoring support in those regions, results in undesired deformation of the cabinet walls thereat.
Due to rising material costs, it is desirable to manufacture insulated appliance cabinets having cabinet walls as thin as possible with the least expensive material possible. However, concern for bulging at the corners associated with current designs imposes a significant limitation on insulation injection pressure and cabinet wall design parameters such as wall thickness and material selection. These limitations result in significantly increased manufacturing cost and time, due to the need to inject foam under relatively low pressure and the need to provide relatively thick cabinet walls. Accordingly, it is desirable to provide a plug to support the inside configuration of an appliance cabinet during the injection and curing of insulating foam which provides the requisite support of the entire cabinet interior, particularly at the corners.
It is also important that the plug be collapsible. Collapsibility of the plug is important in that it allows the cabinet to be removed after the insulation injection and curing without damaging any details present in the cabinet interior. That is, the shoring members of the plug are shaped to mate with the internal contour of the cabinet walls. After insulation, it is desirable to remove the shoring panels inward, away from the cabinet walls, so that the cabinet can be removed without tearing out or scraping any details present in the cabinet walls. With current designs, if the shoring panels are proportioned to be large enough to extend to the corners in their expanded position, then it is not possible to retract the panels away from the cabinet wall surfaces without the panels interfering with one another. Thus, it is desirable to provide a plug for supporting a cabinet interior during injection of insulating foam which reconciles the apparent mutually exclusive characteristics of both providing support at the corners when the panels are in an expanded position, and being retractable so that all the shoring panels are drawn away from the interior cabinet surfaces without interfering with or contacting one another.
Another shortcoming of current designs is that current apparatus require utilization of completely separate plugs for each size cabinet, or at least extensive tooling to change from shoring of the interior of one size or shape cabinet to a cabinet having a different size or shape. Also, current designs are limited to generally rectangular cabinets. It is desirable to provide a plug for shoring cabinet interiors which is flexible enough to accommodate cabinets having a wide variety of shapes and sizes with minimal retooling required between runs of different cabinets.
Furthermore, it is desirable to provide such a plug which is capable of automated operation, thereby allowing large scale assembly line type production.